Pressure induced effects on the chemical and magnetic structure of spinel MnV₂O₄

The influence of external pressure (P  ⩽  5 GPa) on both the structural and magnetic ordering in MnV₂O₄ has been investigated using neutron diffraction technique. The volume and the V-V distance decrease with pressure while the c/a ratio increases, suggesting a lowering of the distortion with pressure. Under ambient conditions this compound exhibits a structural transition (T _S) from tetragonal to cubic at ~53 K and a magnetic transition (T _N ) at ~56 K. It is found that with an increase in pressure to 5 GPa, T _N increases (from 56 K to 80 K), dT _N /dP  >  0, while T _S decreases (from 53 K to 37 K). The non collinear magnetic structure in the tetragonal phase at 5 GPa and 10 K remains the same as at ambient pressure. However, the Mn and V sublattice, now exhibits distinct transition temperatures, [Formula: see text] ~ 80 K, and [Formula: see text] ~ 60 K. The transition to the cubic phase at T _S is accompanied by a collinear alignment of the Mn and V spins and a reduction in the Mn moment. The region in which the structure remains in the cubic phase with collinear magnetic structure increases with pressure from ~3 K at ambient pressure to ~43 K at 5 GPa pressure.